In diagnosing and treating malignant tumors, medical physicians all over the world have tried to create innovative devices designed to treat cancerous tumors in humans. At one time cancer could only be diagnosed when a tumor was big enough to see or feel. Now sophisticated imaging systems can identify tumors far earlier, often before any symptoms have even appeared thereby allowing for early treatment and potential cure. Over the years many different methods have been developed to treat cancer. For breast cancer, surgical approaches such as radical mastectomies were used to remove the breast, chest muscles and underarm lymph nodes—and were occasionally performed as early as the 19th century. The late 1940s brought the modified radical mastectomy, which spared the muscle tissue of the patient. In the 1970s, a more limited surgical option came into use, known as Breast Conservation Surgery, which focused on removal of the tumor and a small amount of surrounding tissue commonly referred to as a lumpectomy. In 1985, the lumpectomy combined with whole breast radiation therapy was found to be as effective as the mastectomy in terms of survival rates, but resulted in higher local relapse rates. As a result, medical research looked to provide other forms of combined surgical and localized radiation treatment options.
At the beginning of the 20th century, shortly after radiation began to be used for diagnosis and therapy, it was discovered that radiation could cause cancer as well as cure it. Many early radiologists used the skin of their arms to test the strength of radiation from their radiotherapy machines, looking for a dose that would produce a pink reaction (erythema) that looked like sunburn. They called this the “erythema dose,” and this was considered an estimate of the proper daily fraction of radiation. In retrospect, it is no surprise that many developed leukemia.
Today, a lumpectomy is a common surgical procedure designed to remove a discrete lump, usually a benign or malignant tumor from an affected woman's breast or in rare occasions a man's breast. As the tissue removed is generally quite limited and the procedure relatively non-invasive, compared to a mastectomy, a lumpectomy is considered a viable means of “breast conservation” or “breast preservation” surgery with all the attendant physical and emotional advantages of such an approach.
In the past a few breast balloon brachytherapy devices have been developed. The most common types available are the Contura® a multi-lumen balloon breast brachytherapy device, and the MammoSite® breast brachytherapy device. Both devices are used in a procedure known as Accelerated Partial Breast Irradiation. Each device contains certain design drawbacks which will be described in the detail below.
An example of a brachytherapy applicator may be the “MammoSite® Radiation Therapy System” developed by Proxima Therapeutics, Inc., Alpharetta, Ga. 30005 USA. The MammoSite® RTS, a balloon catheter which is used in a high dose rate radiation procedure, was introduced specially for use in partial breast irradiation. The MammoSite catheter is inserted at the time of lumpectomy or within 30 days following surgery, remains in place during treatment and is deflated and removed at the end of treatment with mild pain medication. A solid radiation source is typically used; however, a liquid radiation source may also be used with a balloon device placed within a body cavity (e.g., Iotrex®, Proxima Therapeutics, Inc.) The solid radiation source may be removed following each treatment session, with the liquid source remaining in place as long as the balloon remains within the body cavity.
Clinical trials have shown efficacy of inflatable treatment delivery devices and systems such as MammoSite® RTS and similar devices and systems (e.g., GliaSite® RTS, Proxima Therapeutics, Inc.). However, radiation treatment delivered via these devices and systems can have deleterious effects on healthy tissue while providing the desired effects on cancerous tissue due to limited dose optimization inherent in the design. In a radiation treatment, care must be taken to direct the maximum therapeutic dose to diseased tissue while minimizing radiation dose to healthy tissue. For example, radiation treatment may be most effective when all surrounding tissue regions receive the same dose of radiation, and where the radiation dosage received by more distant tissue is as small and as uniform as possible. However because tissue cavities typically are not uniform or regular in their sizes or shapes and may be near critical structures such as skin, lung, or heart, radiation delivered via the aforementioned inflatable delivery devices can result in less than optimal dosages to different regions of surrounding tissue, creating “hot spots” and regions of relatively low dosage “cold spots”.
In an effort to address this problem, another inventor has developed devices and systems to effectively draw adjacent tissue near a treatment device and thus enhance the treatment of the surrounding tissue (U.S. Pat. No. 6,923,754 B1 to Lubock, U.S. Pat. No. 6,955,641 B2 to Lubock). The Lubock patents described devices and systems that utilize vacuum to draw tissue surrounding a body cavity towards a treatment device placed within. The Lubock devices add a sheath or a fluid-permeable enclosure wall and a vacuum conduit to the Mammosite RTS or similar inflatable treatment delivery devices. These added elements create suction around the device, which draws tissue against the device surface within a body cavity, insuring a closer contact between the tissue and the device. Lubock devices claim that they can urge tissue into a desired orientation and position and form a uniform and controlled surface. This control over the distance, spacing, and the amount of tissue contact offers some advantages to the treatment of lining a body cavity.
However, despite small improvements, Lubock patents like the other prior arts, failed to provide physicians with better control over the optimization or shaping of the radiation dose within a body cavity. A common shortcoming of these applicators is that the source can only travel in or near a central catheter or centralized set of catheters within a cylindrical, or spherical balloon applicator. The existing balloon catheters only allow an offset from the center shaft of approximately 0 mm to 5 mm. Such designs limit the ability to maximize dose conformality and homogeneity which can only be maximized by allowing the treatment catheters to be placed significantly farther away from the central position. For example, after a surgery, doctors may find that the cavity wall is near sensitive regions which may have a higher sensitivity to radiation damage, including development of new cancerous tissue, than other areas surrounding the resection cavity. Doctors are always looking to deliver the maximum prescribed dose to the target region while minimizing dose to critical structures. Therefore, there is a need in the art to move the treatment catheters farther away from the central shaft of the balloon device to provide enhanced dose conformality, or dose shaping, allowing for greater flexibility in dose delivery to both target structures as well as those regions where reduced dose would be beneficial.
Design of intra-cavity applicators for brachytherapy is a challenging process, as the bio-mechanical and radiation dosimetry properties of the applicators must be such that they minimize the trauma to the patient during applicator insertion process; that they allow optimal radiation dose conformality to the tumor tissues; and that they provide adequate mechanical strength such that the location of the applicator is predictable throughout the course of treatment. Developments in medical imaging, such as CT, MRI, and PET imaging, have provided clinicians with means to identify tumors on patient images at earlier stages with increased confidence. The technical means to deliver this enhanced conformal dose however is currently severely limited by the available applicators. The present invention aims to overcome these limitations in order to achieve optimal radiation dose distribution to a variety of tumors in or near body cavities.